DSP BASED DIGITAL FM DEMODULATION FOR GMSK SIGNALS PDF

This is the traditional discrete signal FM demodulation method, and it is based on copyrighted material from “Understanding Digital Signal. this with digital signal processing. In an earlier semester project, four FM demodulation algo- are are implemented on the DSP (TMSCDSK). radio provider organizations are planning to replace their traditional analog FM-based. the demodulation of signals that follow the AM-FM model. Traditional such as CPM, CPFSK, FSK, MSK, GMSK and other forms of digital modulation, can be reformulated as digital FM mod- ulation and component AM-FM signal demodulation. The ESA and . threshold around Yo = dB the MESA-based demodu-.

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The method of claim 26 including the step of multiplying said first signal by a first correction signal providing a first product signal and multiplying said second signal by a second correction signal providing a second product signal.

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The signals output from low pass filters and being the sine and cosine representations of a reference angle, are passed to an arc tangent calculator in the correction signal unit demodukation The method of demodulating recited in claim 7 wherein the step of computing the correlation, C Dis performed according to EQU Method and apparatus for obtaining initial carrier and symbol phase estimates for use in synchronizing transmitted data.

The IF 4 is coupled to two multipliers 7 and 8 which are used to produce an in-phase base-band demoxulation and a phase-quadrature base-band signal. The method of claim 26 including the step of multiplying said second signal by a first correction signal providing a third product signal and multiplying said second signal by a second correction signal providing a fourth product signal.

The information bit stream is determined by the following differential decoding: The demodulator recited in claim 4 wherein said matched filter, said non-coherent correlator and said maximum likelihood decision logic are implemented with a dsl signal processor.

The demodulator recited in claim 1 wherein said matched filter filters the sampled received signal according to EQU13 where EQU The output d k is also fed to function block 27 where differential decoding and bit mapping are performed to derive output d krsp is the demodulated information bit stream. Method and apparatus for real-time demodulation of a GMSK signal by a non-coherent receiver. The method of claim 16 further including the step of mathematically squaring said first and second signals and providing in-phase and quadrature portions of said first and second signals.

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Having thus described our invention, what we claim as new and desire to secure by Letters Patent is as follows: Other delay factors might be contemplated as well.

USA – DSP-based GMSK coherent detector – Google Patents

Method for signal transmission using spectrally efficient orthogonal modulation. Year of fee payment: This signal is first passed though matched filter 13 before being supplied to non-coherent correlator A method of detecting in-phase and quadrature components of an information signal comprising: The signal from antenna 10 is amplified in amplifier 11 and then subject to down conversion in down converter 12 to recover signal z k.

Even though coherent demodulation is generally considered the best demodulation for GMSK modulated signals, the performance is not guaranteed under fading channel conditions. The first multiplier 7 ds the IF 4 and multiplies it by a signal obtained from a local oscillator 5 running at the IF frequency. The detector of claim 14 including means for summing said third and fourth product signals providing the quadrature corrected data signal.

The detector of claim 1 wherein the correction signal means includes means for multiplying said in-phase coherent and quadrature coherent signals by said clock signal producing, respectively, an in-phase coherent carrier component and a quadrature coherent carrier component. In function block 22, the samples are subjected to matched filtering with a matched filter.

The method of claim 16 including the step of temporally delaying said first and second signals before producing detected in-phase and quadrature components. The detector of claim 12 including means for demkdulation said first product signal with said second product signal providing the in-phase corrected data signal.

US5131008A – DSP-based GMSK coherent detector – Google Patents

The device of claim 11, wherein said correlator computes a first correlation by summing a sequence of multiplications of the output of the matched filter with a first correlation cor based on at least one previously selected bit. The foregoing and other objects, aspects and advantages will be better understood from the following derailed description of a preferred embodiment of the invention with reference to the drawings, in which:.

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The output of multiplier and are both added in the summer which yields the phase quadrature signal component Q, as shown. The base-band in-phase signal component is multiplied by sine gsmk in a first multiplier The detector of claim 8 including means for calculating the cosine and sine of said correction angle producing first and second correction signals respectively.

US USA en The demodulator implements a dihital, maximum likelihood ML search over multiple bit-time intervals.

This type of receiver usually includes two parts; a first portion that demofulation the bit clock and phase of the signalling tones, and a detector that uses the extracted signal phase. Field of the Invention The present invention generally relates to demodulators for denodulation systems and, more particularly, to a new non-coherent demodulator for a digital communication system which exhibits superior performance in a fading channel. For the demodulator design according to the present invention, the second interpretation is used.

If the baseband signals are raised to the fourth power, the correction signal unit 40 will have to divide the output of the arctangent calculator by four. The method of claim 22 further including the step of calculating the arctanagent of the sine signal divided by the cosine signal producing a first correction angle signal.

The baseband in-phase and phase quadrature signal components are digitized and coupled to a digital signal processor, DSP where the clock and data signals are recovered.

Method of demodulation in digital communication systems with multipath propagation.